To backtrack just a bit, according to fire standards, a hotel is able to have accessible rooms as high as the eighth floor. Apparently, a fire truck ladder can reach that high and a fireman would carry the disabled person out a window and down the ladder. Anything higher than the eighth floor is supposed to be illegal. However, as a person who uses a wheelchair for mobility, I can tell you that I've stayed in "wheelchair accessible" rooms above the eighth floor, so I know many hotels don't comply.
At Disney, I tend not to request a wheelchair accessible room as I'm more inconvenienced by having water everywhere and having no counter space than I am by having a bathroom I can't quite fit my chair into.